I can not imagine what one could possibly need $300,000 per year for unless an apartment costs like $200,000 per year.
When I used to visit the Meta campus in Menlo Park, the QA folk I worked with were commuting 2 hours each way just to be able to afford housing. I've no idea how far away the janitorial staff must have lived to do the same
Being able to afford unpredictable expenses and not have it bankrupt you. In the US, that would include healthcare. Everywhere in the world, that would be useful if you were laid off.
Not really a tenable long-term situation for a senior employee with plans to start a family. Family homes of decent size and area are literally millions of dollars.
To some extent, maybe, but often not. For example, London has similar cost of living to the Bay Area, and when I was at Meta experienced folks like Dan Abramov over in London were making about the same as fresh college hires in Menlo Park...
To be fair though, Dan specifically is kind of notorious for messing up his comp negotiation. Did you not see the Twitter pile on at the time?